Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
  • H04B1/69—Spread spectrum techniques
  • H04B1/707—Spread spectrum techniques using direct sequence modulation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B2201/00—Indexing scheme relating to details of transmission systems not covered by a single group of H04B3/00 - H04B13/00
  • H04B2201/69—Orthogonal indexing scheme relating to spread spectrum techniques in general
  • H04B2201/707—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation
  • H04B2201/70703—Orthogonal indexing scheme relating to spread spectrum techniques in general relating to direct sequence modulation using multiple or variable rates
  • H04B2201/70705—Rate detection

Definitions

• the present invention relates to spread spectrum communications systems, and more particularly, to transmission and reception processing of information
• CDMA code division multiple access
• DS direct sequence
• FH frequency hopping
• variable data throughput rates For example, CDMA transmitters and receivers
• each channel possibly requiring a different data transmission rate.
• CDMA transmitters and receivers sometimes must alternately
• the transmitter must either fill outgoing data frames
• DTX discontinuous transmission
• UMTS Universal Mobile Telecommunications System
• IMT-2000 International Mobile Telecommunications in the year 2000
• variable data rates are achieved by applying a variable per-packet spreading factor (e.g. , variable-rate data symbols are spread using
• PN constant rate pseudo-noise
• spreading factor used for each particular data packet is included in, and transmitted with, the data
• the spreading factor is typically transmitted via a number
• despreaders include very large memory buffers and are therefore rather costly and
• the present invention fulfills the above-described and other needs by
• successive CDMA frames are
• CDMA standards e.g., the above described UMTS/IMT-2000 standard
• CDMA receiver rather than having to collect all of the incoming PN chips for a
• a CDMA despreader according to the invention despreads
• despread data symbols are stored to memory (e.g., within a deinterleaver or error
• the stored data symbols are taken to be temporary, or soft,
• transmitter for transmitting a succession of source data frames, each source data
• each source data frame including a sequence of source data symbols, and each source data frame
• each spreading sequence provides one of a
• rate information is included
• each source data frame including a sequence of source data symbols, and each source data frame being intended for a distinct
• recipient includes the steps of: spreading each source data symbol within a source
• each spreading sequence providing one of a plurality of possible
• frames for a particular recipient is an arithmetic combination of multiple copies of
• a second, lower-order spreading factor used in spreading data frames for the particular recipient.
• receiver mcludes: a despreading processor for despreading an incoming spread
• the incoming data frame includes rate
• the exemplary receiver can further include a deinterleaver, and the deinterleaver can be used as the memory
• transmitting the data frame includes the steps of: despreading an incoming spread
• the memory can be, for
• a deinterleaver in a spread spectrum receiver For example, a deinterleaver in a spread spectrum receiver.
• Figure 1 depicts an exemplary spread spectrum transmitter in which
• variable rate spreading techniques according to the invention can be implemented.
• Figure 2 depicts an exemplary spread spectrum receiver in which variable
• FIG. 3 depicts an exemplary spreading and modulation processor
• Figure 4 depicts a number of exemplary orthogonal channelization
• Figure 5 depicts an exemplary method of despreading spread spectrum data packets according to the invention.
• Figure 6 depicts two exemplary spread spectrum data packets according to
• each data packet incorporating a different spreading factor.
• FIGS. 1 and 2 depict, respectively, an exemplary CDMA transmitter 100
• 100 includes an error detection and correction coding processor 110, an
• interleaver 120 interleaver 120, a spreading and modulation processor 130, and a transmit antenna
• the exemplary receiver 200 includes a receive antenna 210, a
• a data source signal is applied to an
• the receive antenna 210 is coupled to an input of the demodulation and
• despreading processor 220 and an output of the demodulation and despreading processor 220 is coupled to an input of the deinterleaver 230. Additionally, an
• output of the deinterleaver 230 is coupled to an input of the error detection and
• decoder 240 represents a recovered source data output signal.
• source data symbols e.g., successive bits
• the interleaver 120 to provide a stream of coded data symbols to the spreading
• the interleaver 120 then scrambles the time order of
• process and the interleaving process can be either convolutional or block based.
• processor 130 can include data for a number of different channels. Typically, the
• coded bit stream includes a succession of multiple-bit frames, each frame being associated with a specific logical and physical channel (and thus being intended for
• the spreading and modulation processor 130 processes the coded data
• the spreading and modulation processor 130 spreads each coded data symbol in an
• PN pseudo-noise
• the spreading process has the effect of spreading
• spread spectrum signals are received at the receive antenna 210, and the demodulation and despreading processor 220
• modulation process i.e., using known PN sequences for particular users and
• each data symbol can actually be despread
• each delayed spread spectrum signal merely appears as a distinct CDMA channel (due to the
• the receiver can obtain the PN spreading sequences.
• a receiver which is configured
• the deinterleaver 230 After demodulation and despreading, the deinterleaver 230 and the error
• detection and correction decoder 240 process the recovered coded data symbols to
• the deinterleaver 230 is
• deinterleaver memory can be utilized for efficient variable-rate despreading.
• Figure 3 depicts an exemplary direct
• sequence spreading and modulation processor 300 which can be used, for
• the exemplary DS processor 300 includes a parallel-to-serial converter
• first and second channelization multipliers 320, 325 first and second
• randomization multipliers 330, 335 randomization multipliers 330, 335, first and second pulse shaping filters 340, first and second modulation mixers 350, 355 and a combiner 360.
• first and second outputs of the converter 310 are coupled to first inputs
• PN CH a channelization spreading sequence
• randomizing, or scrambling, spreading sequence PN SC is applied to second inputs
• first and second randomization multipliers 330, 335 are coupled to inputs of the
• first and second pulse shaping filters 340, 345 are included in the first and second pulse shaping filters 340, 345.
• outputs of the first and second pulse shaping filters 340, 345 are
• An in-phase carrier signal cos( ⁇ t) is coupled to a second input of the first modulation mixer 350, and a quadrature carrier signal sin( ⁇ t) is coupled
• first and second modulation mixers 350, 355 are coupled to first and second inputs
• spread spectrum transmit signal (e.g., for input to the antenna 140 of Figure 1).
• processor 300 of Figure 3 performs direct sequence
• QPSK quadrature phase shift keying
• the converter 310 receives successive data bits and provides pairs of
• Each bit is then spread, via the channelization and scrambling multipliers 320, 325, 330, 335, using a
• channelization sequence PN ch and a randomization or scrambling sequence PN SC .
• the dual spread bit streams are then shaped via the pulse shaping filters 340, 345
• BPSK binary phase shift keying
• the dual BPSK signals are then combined via the combiner 360, and the resulting
• QPSK signal is transmitted to one or more CDMA receivers (e.g. , via the transmit
• each CDMA channel uses a different channelization
• the channel codes and the channels themselves are synchronized, as is also well known).
• the channelization codes are selected from a set of orthogonal
• variable spreading factor codes (OVSF) which provide for variable data
• a CDMA despreader include a buffer sufficient to store data
• Figure 4 depicts an OVSF code tree 400 including a known set of
• channelization sequences c n m where n and m are integers representing the
• each user can, according to convention, actively use a particular code only if no other code on the path from that code to the root of the tree, or in
• each code in the tree 400 is a subset of all codes in the sub-tree
• code e.g. , c 2>1 is a subset of both c jl and c 4>2 , and c 22 is a subset of both c 4 3 and c 44 ).
• c 2>1 is a subset of both c jl and c 4>2
• c 22 is a subset of both c 4 3 and c 44 .
• each code having a higher spreading factor i.e., a slower data throughput rate.
• spreading factor can be constructed as an arithmetic combination of multiple codes
• a CDMA despreader can be constructed to operate properly without
• incoming chips can be
• frame reception begins at a step
• incoming data symbols are despread assuming a minimum allowable spreading rate (or, equivalently, a maximum allowable data rate).
• rate information symbols within the data frame are interpreted, and a determination is made, at step 530, as to whether
• despreading is complete (i.e. , whether the frame was indeed spread using the
• step 570 ends at step 570. Otherwise, the stored data symbols are first combined, at step 570.
• incoming data frame consists of twenty chips (including either ten or five data
• a first variant 610 (corresponding to a spreading rate of 2) is
• a second variant 620 (corresponding to a spreading rate of 4) is shown to include five data symbols B1-B5 and one rate information symbol RI.
• the short channelization code which is used to spread each symbol is
• the despreader can despread incoming data symbols using the minimum spreading factor of 2 and the corresponding spreading
• each pair of temporary symbols obtained by the first despreading operation can be
• the first data symbol at spreading rate 4 can be obtained as the first
• final combination can be made, for example, directly in the deinterleaver 230.
• the present invention provides CDMA spreading and despreading techniques which eliminate the need for frame-length chip buffers
• successive CDMA frames are transmitted with variable spreading
• each transmitted frame thus including a variable number of data
• channelization spreading sequences used for higher data rate frames are
• demodulation processor despreads incoming chips using a minimum allowable spreading rate. Thereafter, upon receiving the rate information symbols included
• variable rate primarily with reference to direct sequence CDMA systems

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)

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• 1999
  • 1999-12-21 US US09/468,111 patent/US6532250B1/en not_active Expired - Lifetime
• 2000
  • 2000-12-15 JP JP2001550888A patent/JP2003519953A/ja active Pending
  • 2000-12-15 CN CN00817614A patent/CN1413393A/zh active Pending
  • 2000-12-15 WO PCT/EP2000/012766 patent/WO2001050620A1/en not_active Application Discontinuation
  • 2000-12-15 AU AU30123/01A patent/AU3012301A/en not_active Abandoned
  • 2000-12-15 EP EP00990761A patent/EP1240725A1/de not_active Withdrawn
  • 2000-12-18 MY MYPI20005930A patent/MY124718A/en unknown

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